The required minimum strength of modular, ceramic ball heads is ensured by means of a so-called proof test (100%-check). Thereby the conical area of the ball head is hydraulically stressed. This is described in DE 44 11 508 C2.
In view of the special geometrics of modular ball heads, under relevant, oblique in-vivo loads, high tensions can occur in the area of the cone inlet.
According to present-day knowledge there is still no method (proof test), which checks the cone inlet of modular ball heads and guarantees the required minimum strength within the scope of a 100%-check for this area. 100%-check means, that ball heads with defects break up in the proof test, so that only flawless ball heads pass the proof test.